Sub Test()
    With Selection
        If .OMaths.Count = 0 Then 'This means the selection isn't inside a formula
            .TypeText Text:=" " 
            .MoveLeft Unit:=wdCharacter, Count:=1 
            .Font.Superscript = wdToggle
        Else 'Anything that isn't 0 means you're selecting something inside a formula
            .OMaths(1).Functions.add Range:=Selection.Range, Type:=wdOMathFunctionScrSup
            .MoveRight Unit:=wdCharacter, Count:=1 
        End If
    End With
End Sub